That was largely because Bob Mueller’s 16-lawyer Russia probe—which is targeting him—has shifted its focus and is drilling down on tax issues, which aren’t WilmerHale’s specialty. But the parting of ways with WilmerHale was also in part because Manafort’s finances are increasingly strained, according to sources familiar with the situation.

“Paul Manafort’s resolve is limitless, but his resources are not,” said a person close to Manafort.

Manafort isn’t the only person facing financial challenges because of the legal costs of responding to Mueller’s probe. Michael Flynn, the retired general and deposed National Security Adviser, is struggling mightily with his mounting legal bills, according to a source familiar with his situation. The expenses has put his family’s finances under significant duress, the source said, and it’s expected he will soon create a legal defense fund to keep from going bankrupt.

Hiring the high-powered Washington lawyers necessary to respond to a deep-dive Justice Department investigation can be extraordinarily costly. And Manafort—despite his past lucrative contracts with foreign governments, and despite the fact that he owns numerous properties around the country—is feeling the pinch. Sources say that’s part of the reason he is no longer retaining WilmerHale; the firm is known for handling Congressional investigations, but Mueller’s probe has now shifted its focus to international tax issues—which meant Manafort needed lawyers with that expertise. So he has brought in Miller Chevalier, a boutique Washington law firm full of international law experts, and has parted with WilmerHale.